The present invention relates to a mechanical transmission member of the type comprising an inner race ring, an outer race ring surrounding the inner race ring and means of coupling the inner and outer race rings together, allowing them to pivot relative to one another about their common axis, the coupling means comprising means for axially retaining the outer race ring with respect to the inner race ring, these retaining means comprising at least one axial thrust washer which interacts with an annular groove radially on the inside of the outer race ring and with a surface which is axially on the outside of the inner race ring.
The invention applies in particular to tripod constant-velocity mechanical joints for motor vehicle transmissions.
These tripod constant-velocity joints generally comprise a male element with ternary symmetry, or tripod, secured to a first rotating shaft, and a female element with ternary symmetry, or bell housing, secured to a second rotary shaft.
The male element has three arms and the female element delimits three pairs of runway tracks. A mechanical transmission member of the above-defined type is mounted on each arm of the tripod.
The inner race ring of a mechanical transmission member such as this rolls and slides along the corresponding arm. The outer race ring is a roller intended to run along the corresponding pair of tracks to allow the constant-velocity joint to operate when the two rotary shafts are out of alignment, forming an angle between them.
The connection between the inner race ring and the outer roller needs to be a connection which allows free rotation about their common axis and translation along this axis, which translation is restricted to a clearance needed for assembly.
Rotation about the common axis of symmetry is allowed by rolling-bearing means, generally of the needle-bearing type, arranged between the inner race ring and the outer roller. The means of axial retention, for their part, prevent substantial translation, along the axis of symmetry, of the inner race ring and of the outer roller.
Hitherto, these means of axial retention comprise, for each mechanical transmission member, two thrust washers which are flat, elastic and split washers. Of each thrust washer, its peripheral edge is housed in an annular groove in the outer race ring and one of its surfaces bears against the corresponding axially outer surface of the inner race ring. The grooves in the roller are of rectangular cross section and therefore weaken the rollers.
The thrust washers are very rigid and need to hold very tight tolerances which are associated directly with the dimensions of the grooves in the outer roller, so that once the transmission member has been assembled, the split thrust washers are practically closed up.
Manufacturing the grooves and the thrust washers, and fitting the latter into the grooves in the outer rollers, which entails special-purpose equipment, are expensive operations.
The object of the invention is to solve these problems by providing a mechanical transmission member of reduced weakness and reduced manufacture and assembly cost, in particular allowing manual assembly of its constituent parts.
To this end, the subject of the invention is a mechanical transmission member of the aforementioned type, characterized in that the means of axial retention further comprise at least one elastic snap ring, especially a split ring, interacting with a retaining surface which is axially on the outside of the groove and with a bearing surface of the thrust washer for axially retaining the latter.
According to some particular embodiments of the invention, the mechanical transmission member may have one or more of the following features, taken in isolation or in any technically feasible combination:
the elastic snap ring is of approximately circular cross section;
the retaining surface of the corresponding groove converges axially towards the outside of the member, and the bearing surface of the corresponding thrust washer converges axially towards the outside of the member to a lesser extent than the said retaining surface;
said bearing surface is extended axially towards the outside of the member by a surface for insertion of the said snap ring, this insertion surface converging axially towards the outside of the member at an angle which is at least equal to that of the said retaining surface of the groove;
said retaining surface and the said bearing surface are approximately frustaconical;
said thrust washer has concaveness facing axially towards the outside of the member and at least part of the peripheral edge face of this thrust washer constitutes the said bearing surface;
said thrust washer has concaveness facing axially towards the inside of the member and part of the axially outer surface of the said thrust washer constitutes the said bearing surface;
the member is intended to be mounted on an arm about which the inner race ring rolls and slides, and the member further comprises at least one element projecting radially towards the inside with respect to the inner race ring, for axially retaining the member on the arm;
the said retaining element is a retaining washer which, on the one hand, is held between the thrust washer and the corresponding axially outer surface of the inner race ring and, on the other hand, is intended to interact with the said arm to provide the said axial retention; and
the radially outer edge of the said retaining washer is housed in a counterbore of the radially inner edge of the corresponding thrust washer.
A final subject of the invention is a constant-velocity mechanical joint, comprising a male element comprising several arms, a female element delimiting two race tracks for each arm and, for each arm, a mechanical transmission member mounted on said arm, this mechanical transmission member comprising an inner race ring that can swivel about said arm, an outer race ring forming a roller surrounding the inner race ring and rolling along the two associated race tracks of the female element, and means for coupling the race ring and the roller in a pivoting way allowing relative pivoting about their common axis, characterized in that at least one mechanical transmission member is a mechanical transmission member as defined hereinabove.
The invention will be better understood by reading the following description given merely by way of example and made with reference to the appended drawings in which:
FIG. 1 is a view in cross section of a mechanical tripod constant-velocity joint according to the invention,
FIG. 2 is an enlarged view of circled part II of FIG. 1, illustrating the cross section of one mechanical transmission member of the joint,
FIG. 3 is an enlarged view of circled part III of FIG. 2, illustrating the assembly of the transmission member of FIG. 1,
FIG. 4 is a view similar to FIG. 3, illustrating the operation of the retaining means of the transmission member of FIG. 3,
FIG. 5 is a view similar to FIG. 2, illustrating an alternative form of the transmission member of FIGS. 1 to 4, and
FIGS. 6 and 7 are views similar to FIG. 3, schematically illustrating other alternative forms of the mechanical transmission member of FIGS. 1 to 4.